This is a phase of an investigation of the proximate cause(s) of sperm-induced abnormal development of chicken embryos such as result from high-oviduct insemination and from aged spermatozoa. Specifically the possible production of parthenogenic and/or gynogenic embryos are being explored by examining embryos in early cleavage stages produced tritiated-thymidine-labeled spermatozoa and by gel-electrophoresis of hemoglobin of embryos from hens inseminated with semen from mutant cocks.